NPR has an interview with Giles Martin on the upcoming reissue of the Beatles' Hollywood Bowl recordings. You can hear some additional music off the new album, too.
"There's a guy who works in IT here who's developing de-mix technology, you know, being able to take one track and separate it into its constituent parts. I'd been playing around with him with this for a while and I said, 'Why don't we try it on screams from the Hollywood Bowl.' And we tried it and what we ended up with is it split the one track into two tracks and you get the screams on one half and then you have this weird, almost like the band playing but it sounds a little strange. But this meant we could go into, for instance, the drum track and bring out the best of the drums, as opposed to what my father had. If he did [anything] to the drums he'd be doing it to the screams as well. So we could basically clean up the recordings. And it's always my ambition to make people feel as though they're there watching the band. Now what you have with Hollywood Bowl is you're much closer to the band."